BatchUpdateTest: Use fake index by default

Change-Id: I5edb10faf2c9b6c1c62c1f2da48a25853b1cc042
diff --git a/javatests/com/google/gerrit/server/update/BatchUpdateTest.java b/javatests/com/google/gerrit/server/update/BatchUpdateTest.java
index 287a7fe..10599c6 100644
--- a/javatests/com/google/gerrit/server/update/BatchUpdateTest.java
+++ b/javatests/com/google/gerrit/server/update/BatchUpdateTest.java
@@ -64,6 +64,7 @@
             cfg.setInt("change", null, "maxFiles", 2);
             cfg.setInt("change", null, "maxPatchSets", MAX_PATCH_SETS);
             cfg.setInt("change", null, "maxUpdates", MAX_UPDATES);
+            cfg.setString("index", null, "type", "fake");
             return cfg;
           });